In the field of web perforation, and particularly when very high accuracy is required in positioning the perforations, it is necessary to have such reciprocating motion in a plane. Thus, the French patent application No. 9,003,697 filed Nov. 19, 1990 and entitled Device for Carrying Out an Operation on a Web according to a Given Pitch, corresponding to uncurrently filed, allowed U.S. Ser. No. 07/927,501, describes a device comprising a punch block support arm describing, in an reciprocating manner, a short portion of an arc of a circle around a stationary horizontal axis parallel to the movement axis of the web, so as to be able to cause the punches do cooperate periodically with a die provided on a die block. The punch block support arm is connected to the die block at the level of the stationary horizontal axis, the two blocks connected in this way being driven parallel to the movement axis of the web by a reciprocating movement of a generally identical period to that of the movement of the punch block support arm around the stationary axis. In these perforators, the period of the reciprocating movement can be in the order of 37 ms for a magnitude of approximately 20 mm.
For such devices, combining at the same time speed and accuracy, it is of great importance that the horizontal reciprocating movement be exactly parallel to the plane of the web and that the movement be constantly carried outin the same plane.
In the previous technique, it was known to use crank-connecting rod mechanisms, which could be of the eccentric type, to produce such reciprocating movement, the movement being guided in a same plane by means of suitable sliding mechanisms. For very high frequency reciprocating movements, these mechanisms suffered from quite fast wear, making the guiding movement increasingly inaccurate. Furthermore, such guiding mechanisms often generated jerks in the reciprocating movement. Such jerks are, of course, detrimental to the accuracy of positioning perforations on the web.